src/base/value_schema_manager.cpp

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

#include "value_schema_manager.h"
#include "value_schema_v0.h"
#include "value_schema_v1.h"
#include "value_schema_v2.h"

#include <dsn/utility/endians.h>
#include <dsn/dist/fmt_logging.h>
#include <dsn/c/api_utilities.h>

namespace pegasus {
value_schema_manager::value_schema_manager()
{
    /**
     * If someone wants to add a new data version, he only need to implement the new value schema,
     * and register it here.
     */
    register_schema(dsn::make_unique<value_schema_v0>());
    register_schema(dsn::make_unique<value_schema_v1>());
    register_schema(dsn::make_unique<value_schema_v2>());
}

void value_schema_manager::register_schema(std::unique_ptr<value_schema> schema)
{
    _schemas[schema->version()] = std::move(schema);
}

value_schema *value_schema_manager::get_value_schema(uint32_t meta_cf_data_version,
                                                     dsn::string_view value) const
{
    dsn::data_input input(value);
    uint8_t first_byte = input.read_u8();
    // first bit = 1 means the data version is >= VERSION_2
    if (first_byte & 0x80) {
        // In order to keep backward compatibility, we should return latest version if the data
        // version in value is not found. In other words, it will work well in future version if it
        // is compatible with latest version in current
        auto schema = get_value_schema(first_byte & 0x7F);
        if (nullptr == schema) {
            return get_latest_value_schema();
        }
        return schema;
    } else {
        auto schema = get_value_schema(meta_cf_data_version);
        if (nullptr == schema) {
            dassert_f(false, "data version({}) in meta cf is not supported", meta_cf_data_version);
        }
        return schema;
    }
}

value_schema *value_schema_manager::get_value_schema(uint32_t version) const
{
    if (version >= _schemas.size()) {
        return nullptr;
    }
    return _schemas[version].get();
}

value_schema *value_schema_manager::get_latest_value_schema() const
{
    return _schemas.rbegin()->get();
}
} // namespace pegasus